Apparatus for manufacturing high pressure inert gas

ABSTRACT

AN INTERNAL COMBUSTION ENGINE, AT LEAST ONE COMPRESSOR ATTACHED TO AND DRIVEN BY THE ENGINE, A COMBUSTOR TO WHICH THE EXHAUST OF THE ENGINE IS CONDUCTED ALONG WITH GAS AND AIR WHICH IS BURNED IN THE COMBUSTOR, A HIGH TEMPERATURE AIR COOLED HEAT EXCHANGER HAVING AN INLET HEADER, AN OUTLET HEADER, AND FINNED TUBE COMMUNICATING BETWEEN THE HEADERS, THE GAS OUTLET FROM THE COMBUSTOR PASSING THROUGH THE HEAT EXCHANGER, A FAN FOR PASSING AMBIENT AIR BETWEEN THE FINNED TUBE FOR COOLING THE GAS OUTPUT OF THE COMBUSTOR, A CATALYTIC CONVERTER THROUGH WHICH THE GAS IS PASSED BEFORE PASSING TO THE COMPRESSOR, HIGH PRESSURE INERT GAS BEING DELIVERED AT THE COMPRESSOR OUTLET.

United States Patent 3,725,012 APPARATUS FOR MANUFACTURING HIGH PRESSURE INERT GAS George H. Gower, 6120 S. Kingston, Tulsa, Okla. 74135 Filed Jan. 27, 1971, Ser. No. 110,028 Int. Cl. 1301i 7/00 US. Cl. 23-281 6 Claims ABSTRACT OF THE DISCLOSURE An internal combustion engine, at least one compressor attached to and driven by the engine, a combustor to which the exhaust of the engine is conducted along with gas and air which is burned in the combustor, a high temperature air cooled heat exchanger having an inlet header, an outlet header, and finned tube communicating between the headers, the gas outlet from the combustor passing through the heat exchanger, a fan for passing ambient air between the finned tube for cooling the gas output of the combustor, a catalytic converter through which the gas is passed before passing to the compressor, high pressure inert gas being delivered at the compressor outlet.

BACKGROUND, SUMMARY AND OBJECTS OF THE INVENTION An important use of high pressure inert gas is in the petroleum industry where such gas is utilized to assist in the recovery of petroleum. For a background on the method of manufacturing and the use of inert gas reference may be had to the following United States Pats. Nos.: 1,952,005; 2,392,711; 3,000,707; 3,232,885; and 3,389,972. In addition, reference may be had to copending application S.N. 860,908 filed Sept. 25, 1969, entitled Apparatus for Manufacturing High Pressure Inert Gas, now Pat. No. 3,579,308.

In order for inert gas to be effectively utilized as a medium for injection into subterranean formation to augment the recovery of petroleum it is necessary that the gas be injected at high pressures which requires the gas to pass through a sequence of compression steps. At each step the effect of pressure increase raises the temperature of the gas. In addition, the gas is at a relatively high temperature initially. The normal exhaust gas temperature from an internal combustion engine is approximately 600 F. to 1,200 F. The exhaust gas is preferably passed through a combustor wherein fuel and air are mixed with the exhaust gas, and burned to provide a gas output from the combustor substantially free of oxygen. The gas out of such combustor usually has a temperature of 2,000 F. to 2,600" F.

It has been a practice in the industry to utilize liquid cooled heat exchangers for reducing the temperature of the exhaust gas from an internal combustion engine, or from a combustor, and between compression stages, to keep the temperature of the gas from rising to an excessive level. While liquid cooled heat exchangers function satisfactorily they do have several disadvantages. First, in many parts of the world wherein large quantities of petroleum are produced, water is not readily available, particularly in large quantities, and more particularly at a quality satisfactory for use for cooling purposes. Sometimes it is necessary to run a water line for a long distance to provide cooling water for an inert gas injection system, materially increasing the cost of such system. Second, water cooled heat exchangers, by their nature, require a great deal of maintenance. Unless water is carefully treated it can soon build deposits on heat exchanger equipment which drastically reduces the heat transfer efliciency of the equipment.

This invention provides means of eliminating the use of water cooled heat exchangers in an inert gas generating system.

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Another problem with the existing systems for generating inert gas is that of providing high quality inert gas from an internal combustion engine. This invention provides means of controlling a combustor wherein the exhaust of an internal combustion engine is mixed with other fuel for complete combustion, including means of automatically obtaining the proper air mixture for achieving complete combustion.

It is therefore an object of this invention to provide an improved apparatus for manufacturing high pressure inert gas. More particularly, an object of this invention is to provide an apparatus for manufacturing high pressure inert gas wherein the quality of the inert gas produced from an internal combustion engine exhaust is improved.

Another object of this invention is to provide an apparatus for manufacturing high pressure inert gas which does not require water cooling and which thereby eliminates a major source of problems and difiiculties in the operation of known types of inert gas generating systems.

Another object of this invention is to provide an apparatus for manufacturing high pressure inert gas including an internal engine and a combustor, including means of preventing air from being inadvertently draw into the system.

These and other objects of the invention will be fulfilled by the apparatus to now be described in the following specification and claims, taken in conjunction with the attached drawing.

DESCRIPTION OF THE DRAWING The figure is a schematic diagram showing an arrangement of the apparatus of this invention for producing high pressure inert gas utilizing an internal engine and a combustor, and in a manner wherein no cooling water is required.

DETAILED DESCRIPTION Referring to the drawing, the numeral 10 indicates an internal combustion engine, which may be either a two cycle or four cycle type, having an output shaft indicated by the numeral 10A, an exhaust gas outlet 10B, and a fuel intake 10C. The engine 10 drives, among other components, a first stage compressor 12. In its simplest embodiment only one stage of compression may be utilized but in the usual application a plurality of stages are included. For purposes of illustration only a first stage compressor 12 and a second stage 14 are shown, it being understood that as many stages may be driven by engine 10 as required for the specific application.

The exhaust from engine 10 is fed into a combustor 16 having an exhaust gas inlet 16A, a fuel inlet 163, an air inlet 16C, and a gas outlet 16D. In the combustor the exhaust from engine 10 is combined with fuel and air and burnt under conditions to achieve, as near as possible, complete combustion. Such serves two purposes: First, it completes the combustion of the exhaust from engine 10 to eliminate any carbon monoxide or free oxygen content therein, and second, it furnishes additional inert gas for the system.

Gas from combustor 16 is fed to a high temperature air cooled heat exchanger, generally indicated by the numeral 18. The heat exchanger 18 includes an inlet header 18A which receives the intake of gas from combustor 16; an outlet header 18B; and finned tubes 18C extending between inlet header 18A and outlet header 18B. A fan 18D, which may be, as illustrated, driven by engine shaft 10A, serves to pass ambient air through finned tubes 18C to cool the gas flowing therethrough. Gas flowing out of heat exchanger 18C passes to the inlet 20A of a catalytic converter 20. From the catalytic converter outlet 20B the gas passes to a second air cooled heat exchanger 22 which, like first exchanger 18, in-

eludes an intake header 22A, an outlet header, finned tubes 22C, and fan 22D. In heat exchanger 22 the gas is again cooled and passed to inlet 24A of a scrubber 24 and out scrubber outlet 24B. From the scrubber 24 the gas passes to the intake 12A of compressor first stage. Inert gas, which has been treated in the catalyst 22, cooled in finned tube heat exchangers 18 and 22, cleaned in scrubber 24, and pressurized in compressor 12, passes out through the compressor outlet 12B for use as high pressure inert gas.

As previously stated,'the typical application of inert gas in the petroleum industry requires the use of multiple compressor stages. In the drawing one additional compressor stage 14 is illustrated. Since each time gas is compressed heat is generated, successive compressor stages require the gas to be cooled between stages, otherwise the gas temperature will become so high as to make it impractical to handle. Thus a third air cooled heat exchanger 26 is preferably utilized having inlet header 26A, outlet header 26B, finned tubes 26C, and fan 26D all having the purposes previously described relative to the first heat exchanger. From the exchanger outlet header 26B the gas is conducted to a separator 28 wherein any solid or liquid contaminants are removed and the gas is passed to the intake 14A of second stage compressor 14. At the outlet 14B of the second stage compressor high pressure inert gas is available. If the pressure at 14B is not sufficiently high subsequent stages may be utilized and in the preferred arrangement an air cooled heat exchanger is used between each compressor stage.

Fuel, from a source 30, is passed through fuel control valve 32 to the engine fuel inlet 100. In order to maintain the engine C at proper speed, to effectively drive the fans, compressors and so forth, and to automatically increase the fuel consumption as necessary to supply varying inert gas requirements, a governor 34 may be utilized. The governor controls fuel valve 32 to increase the flow of fuel to the engine 10 to maintain the engine speed. A fuel control valve 36 regulates the flow of fuel to combustor fuel inlet 16B. Such valve 36 may also be controlled by governor 34 so that when the governor actuates to increase fuel to the internal combustion engine 10 to the fuel injection into combustor 16 is also increased to make certain that all of the combustible components of the engine exhaust are consumed in the combustor.

In order to provide high quality inert gas it is important that all portions of the system be maintained under positive pressure to prevent air being drawn into the system. Putting it another way, if all portions of the system are under positive pressure any leak which occurs will result in leakage of the gas, reducing only the quantity of gas produced, and not result in the intake of air which would impair the quality of the gas produced. In order to maintain a positive pressure in combustor 16 and in gas outlet 16B thereof, a supercharge 38 is utilized which, like other components of the system, may be driven from engine drive shaft 10A. Supercharger 38 takes air in at 38A and discharges it, under compression, at outlet 38B. The air may flow directly from 38B to combustor air inlet 16C. In the illustrated arrangement however, an air control valve 40 is provided which is regulated by a combustion analyzer 42. The gas at catalytic converter outlet 20B is sampled by the combustor analyzer 42. The flow of air to combustor 16 is regulated accordingly.

It can be seen that in the arrangement wherein the combustor 16 is utilized it is only necessary, to preserve the quality of the inert gas produced, to make sure that no air is drawn into the system from the combustor outlet 16D on through the balance of the system. For this reason the exhaust 10B of the engine 10 is not necessarily under pressure. However, if combustor 16 is maintained above atmospheric pressure the same pressure will exist in exhaust 1013. This may normally interfere with 4 the efficiency of engine 10. If necessary, air from supercharger 38B may be directed to the air intake of engine 10 so that it is supercharged to offset the back pressure of the exhaust to the combustor.

As previously stated it is important to maintain a positive pressure in the system. That is, to provide an arrangement wherein first stage compressor 12 does not pull a vacuum by the effect of gas drawn in through compressor intake 12A. To make sure a vacuum does not occur a bypass valve 44 may be provided, connecting the outlet of compressor 12 back to the compressor inlet. The valve 44 is controlled by pressure at the combustor gas outlet 16D. When the pressure at combustor gas outlet 16D falls below a preselected pressure, which will always be above atmospheric pressure, valve 44 is open to cause gas to be recycled from the compressor outlet back to the compressor inlet to raise the pressure of gas at the compressor inlet. By this system a positive pressure can always be maintained throughout the system from the combustor gas outlet 16D onward.

It can be seen that the apparatus as described fulfills all of the objectives set forth previously. It is important to note that the arrangement eliminates the necessity for use of water cooled heat exchangers. The finned tube heat exchangers 18, 22 and 26 are preferably of the high temperature type utilizing stainless steel or similar tubes having the fins bonded securely thereto rather than merely wrapped around as is utilized in lower temperature type finned coolers. By way of illustration, the temperature at engine exhaust 10B may be in the range of 600 F. to 1,200" F. The temperature at gas outlet 16D of the combustor may be in the range of 2,000 F. to 2,600 F. The temperature of the gas is reduced in heat exchanger 18 so that the temperature of the gas flowing through the catalytic converter may be in the range of l,0O0 F. to 1,200" F. In second heat exchanger 22 the gas is further cooled so that the gas fed through scrubber 24 into the intake 12A of compressor first stage 12 may be at approximately F. Thus the temperature of the gas is reduced in the heat exchanger 18 and 22 from the relative high temperature as it leaves the combustor to the relatively lower temperature preparatory to enter into the first stage of compression. This is achieved without utilization of liquid cooling and the problems attended therewith as previously discussed.

While the invention has been described with a certain degree of particularity it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. For instance, the am rangement of components may vary considerably such that only one of the heat exchangers 18 or 22 may be utilized. The scrubber 24 is not indispensable to the invention in its simplest embodiment, and other refinements described herein may, in many circumstances, be optional. It is understood that the invention is not limited to the specific embodiment set forth herein for exemplification but is limited only to the scope of the attached claim or claims, including the full range of equivalency to which each element or step thereof is entitled.

What is claimed is:

1. Apparatus for manufacturing high pressure inert gas comprising:

an internal engine having an output drive shaft, a fuel intake, and an exhaust;

at least one compressor attached to and driven by said engine drive shaft, the compressor having an intake and an outlet;

21 combustor having a fuel inlet, an air inlet, an exhaust gas inlet, and a gas outlet, said engine exhaust being connected to said combustor exhaust gas inlet;

means of injecting air and fuel into said combustor, the fuel and exhaust from said engine being burned to provide at the combustor outlet a gas low in free oxygen content;

a high temperature air cooled heat exchanger having an inlet header, an outlet header, finned tubes communicating between said outlet and inlet headers, and a fan for passing ambient air between said finned tubes, said inlet header having a gas inlet connected to said combustor gas outlet, and said outlet header having a gas outlet;

a catalytic converter having an inlet and an outlet, the

inlet communicating with said heat exchanger outlet, and the outlet communicating with said compressor inlet, high pressure inert gas being delivered at said compressor outlet.

2. An apparatus for manufacturing high pressure gas according to claim 1 including:

a supercharger having an air inlet and an air outlet, said air outlet being connected to said combustor air inlet, providing said means of injecting air into said combustor.

3. An apparatus for manufacturing high pressure gas according to claim 2 including:

an air valve means between said combustor air inlet and said supercharger air outlet; and

a combustion analyzer connected to sample and respond to the chemical composition of gas passing out of said combustor outlet, said combustion analyzer including means connected to said air valve means for controlling the rate of air injection to said combustor in response to chemical composition of gas passing out of said combustor.

4. An apparatus for manufacturing high pressure gas according to claim 1 including:

means of maintaining positive pressure in said combustor outlet and all parts of the apparatus through which gas subsequently passes to prevent air being drawn into the system.

5. An apparatus for manufacturing high pressure inert gas according to claim 1 including:

a second air cooled heat exchanger having an inlet header, an outlet header, and finned tubes communicating between said inlet and outlet headers, and a fan for passing ambient air between said finned tubes, said inlet header having a gas inlet connected to said catalytic converter outlet and said gas outlet header connected to said compressor intake.

6. An apparatus for manufacturing high pressure inert gas according to claim 1 including:

a scrubber having an inlet and an outlet, the inlet connected to said second heat exchanger outlet, and the outlet connected to said compressor intake.

References Cited UNITED STATES PATENTS 3,389,972 6/1968 Pottharst, Jr. 23-281 2,473,527 6/1949 Hoop 23-281 3,000,707 9/ 1961 Barstow 2325 JAMES H. TAYMAN, IR., Primary Examiner US. Cl. X.R. 

